Little is known about the role of glycosphingoiipids (GSL) in atherosclerosis, which contributes to cardiovascular disease (CVD) and death in ~50% of the population, in the western world. We have observed that the level of a GSL; lactosylceramide (LacCer) and the activity of LacCer synthase (LCS) is increased in human atherosclerotic plaques, as compared to visibly normal tissue. Our preliminary studies also show that atherosclerosis and a marked increase in the level of blood cholesterol can be reveresed by a GSL synthesis inhibitor (D-1-phenyl-2-decanoylamino-3-morpholino-1-propanol; D-PDMP) in a dietary model of hyperlipidemia in rabbits. Our overall goal is to determine whether inhibiting GSL synthesis can ameliorate atherosclerosis in an apolipoprotien E(apoE-/-) mouse model of hyperlipidemia /atherosclerosis. And to determine whether LCS mass can serve as a prognostic marker in CVD. Our specific aims are: 1. To determine the efficacy of D-PDMP in regulating atherosclerosis in apoE-/- mice; herein, the efficacy of D-PDMP in preventing and interfering with atherosclerosis will be examined in mice fed a hyperlipidemic diet, and the following will be measured: cadiac function, carotid intima media thickeness, arterial stiffness, and lipid and lipoprotiens. 2. To determine the molecular mechansim(s) by which D-PDMP regulates atherosclerosis; proteins affecting GSL and cholesterol homeostasis contributing to cell proliferation adhesion and angiogenesis will be measured. 3.To determine the specific roles of Lactosylceramide and LCS in atherosclerosis. We will synthesize novel LCS inhibitors and determine their efficacy in preventing /interfering with atherosclerosis. 4. Quantify the mass of LCS and assess post- transcriptional modification in the heart and artery in normal and atherosclerotic mice. We will develop novel ELISA assays and use mass spectrometry to determine LCS mass and post transcriptional modifiactions. The proposed studies will definitely establish that inhibiting GSL synthesis can inhibit atherosclerosis. It will also prove that LCS can be a novel target for developming drugs to ameliorate CVD and related diseases. Finally, these studies will change our mind-set with regard to the role of GSL in health and CVD. RELEVANCE (See instructions): Although much is known about the role of cholesterol in heart disease, our knowledge about the role of glycosphingolipids in this disease has lagged behind. Herein, we propse to test the hypothesis that inhibiting glycosphingolipid synthesis can decrease blood levels of cholesterol, and ameliorate atherosclerosis and heart disease in animal models. Our studies will lay the foundation for application of novel drug therapy to ameliorate heart disease in man.